package com.sloera.nowcoder;

import java.util.Scanner;

/**
 * class com.sloera.nowcoder
 * user sloera
 * date 2022/2/23
 */
public class HJ107 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextDouble()) { // 注意 while 处理多个 case
            Double a = in.nextDouble();
            boolean positive = false;
            if (a < 0) {
                positive = true;
                a = -a;
            }
            double result = solve(a, 0, (int) (a + 1));
            if (positive) {
                result = -result;
            }
            System.out.printf("%.1f%n", result);
        }
    }

    private static double solve(double a, int left, int right) {
        if (right - left <= 1) {
            for (int i = 1; i < 10; i++) {
                final double rightRound = (left + i * 0.1) * (left + i * 0.1) * (left + i * 0.1);
                if (rightRound > a) {
                    if (a - (left + (i - 1) * 0.1) * (left + (i - 1) * 0.1) * (left + (i - 1) * 0.1) > (rightRound - a)) {
                        return left + 0.1 * i;
                    } else {
                        return left + 0.1 * (i - 1);
                    }
                }
            }
            return a;
        }
        int middle = (left + right) >> 1;
        final int multi = middle * middle * middle;
        if (multi == a) {
            return middle;
        } else if (multi < a) {
            return solve(a, middle, right);
        } else {
            return solve(a, left, middle);
        }
    }
}
